A deadline that is expected to or has already moved. Proper deadlines are immovable because they're "dead"; movement betrays non-deadness, and because deadness is the defining feature of a proper deadline, its absence renders the linedud.
Greg: Right, I'm going down the pub.
Brad: But you haven't finished your coursework essay yet and the deadline's tomorrow morning!
Greg: Chill dude, that's actually a dudline.
Brad: You don't know that!
Greg: Sure I do. Just look at what happened the last two times.
Brad: Hmm, yeah, I suppose you're right.
1. The state of having performed a well-meaning action that inadvertently made things worse
2. The quality of being lovable, but ultimately dispensible
3. Next to cleanliness